docs: def is_netcdf(url):
      '''
      Returns True if the URL points to a valid local netCDF file
  
      :param str url: Location of file on the file system
      '''
      # Try an obvious exclusion of remote resources
      if url.startswith('http'):
          return False
  
      # If it's a known extension, give it a shot
      if url.endswith('nc'):
          return True
  
      # Brute force
      with open(url, 'rb') as f:
          magic_number = f.read(4)
          if len(magic_number) < 4:
              return False
          if is_classic_netcdf(magic_number):
              return True
          elif is_hdf5(magic_number):
              return True
  
          return False